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7 Segmental Motion

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classes in polymer dynamic based on
George Phillies book phenomenology of polymer solution dynamics Cambridge University Press 2011 ends today this
lecture E is
Chapter 6 segmental motion they were going to
discuss chapters 6 unsentimental and I was actually the 1st number officials in Chapter 6 beyond simply moving segments were going to spend some time talking about the fact that treat their
words work teams have been set and we will discuss it as an example of the sort of work the so where we are where we are going to be this was going to start now actually discussing moving polymers doing survival as opposed to so 1st required consider what we can say about Paul emotion and there is a traditional home division of polymer motion in parts of the division of lies incessantly things occur on different timescales but let me draw sketch this can be tolerable during the holidays I'm not sure we the molecular details remained ancient and then off to the side of the site and if for example we have Siberian benzene ring setting now it's actually attached organic compounds over here but I have drawn and what we now ask is how this molecule moves the 1st answer is this is about the same rate as a single bond so we have 3 rotation like this now it's not completely free rotation that is there's a potential energy between the benzene ring back and so to some extent some orientations are preferred also are the extent may not be very strongly you shouldn't think there's no interaction and we can and therefore are clever can actually measure benzene ring rotating around the spot and this happens on a very short time scales but I mean I heard small well because seconds is always nice to you might be on the service but the main issue is as this is the fastest sort process you could get mountain asked Can you get similar processes the main chain and the answer is in general not very easily because of the structure of work structures but here we get something very effects in terms of it's not the a poet physicist analysts all half-century ago tho he was around much more recently and this discussion originally refers to dielectric relaxation which is the next year and this is what is called a high ceiling the next relaxation which is also quite fast but not as fast as this involves the notion but we get from changes this way where the chain those emotions a little hard to do with your hands I just the sort of orientation that you encounter in automobile crashes where there is a peace of ,comma and it is a complicated shapes and it rotates like my hands eroding and the point of the crankshaft rotational let me draw section organic structures of so this is the biggest stretch but overall structure of Europe Alliance government now this long and that Parliament be drawn be lined up which is very simple and of the 1 of which is a little optimistic to think this have cereal you'd get from nations around here and around in there and these moves around like that now a this happens these 2 bombs that I if the parallel this works if they're not parallel things not work of feature also will bonds is not free rotation around here is restricted in the sense that the 2 confirmations that are more favorable unless they but there is no particular reason for this problem to be the mind black workers and not out here someplace .period Torrance you so personal go well as a result this sort of rotation gets quite complicated and inward make it work you actually have to hear things pulling and pushing at greater distances nonetheless you can get rotation like this that America is the federal molecule change the functions of a bond analyst at the Center to accommodate the benzene ring imagined life of the bond of the same name is doing something like this but let me emphasize items saying rotation and the simplest thing to think of rotations for example how trials to Waitsfield on .period or hand on placards the real molecular rotation because the other molecules and what is more complicated than that and if they get a displacement through an angle over some time and that there are changes in speed and maybe even changes in direction so few when asked how molecules reorient just saying things rotate as if they were spending freely is not necessarily completely accurate and affect the motion on long timescales somewhat diffuse light diffusion however the core issue is the direction changes and after a while if you're patient the direction molecules pointing is unrelated to the direction in which stock now we come to the 3rd sort of rotation which is why we have fun directions from 1 carbon to the next and we could get rotation this axis all rotation around the axis pointing this way out of playing like this is stocked maritime the but we could also get rotation in which it wanted time bond pointing this way and a later time bombs .period some other How could you possibly get such emotions while the Socialists here's following molecules measurements as rigid as bent on piece coding region
wired the whole lot of this place like that and if the whole molecule rotates it's not going to spend freely but it will change which rates pointing when the whole molecule rotates it carries along each of the little pieces however there will also be part of a campaign to raise the border here's a molecule that 1 moment in time and here is a little piece of molecule guests molecules are polymer molecules most of them are a flexible rather few molecules that are not flexible rod homeowners that are somewhat status up to totally you can get molecules quite told status DNA is a stiff over a fairly long distances because of the complicated organic the and the net result of saying the molecule sloppy isn't it was like this 1 time at some later time it would be for example like that and as the molecule with also this factor this section of the all who is now facing it's changed direction it's facing because the molecule flocks In the molecules in our region so molecules internal lotions but but but but but but but 2 so there was internal motions of molecules and if we have is the change and we wait awhile some of the time it will be like the I'm not going to draw on the arrow I just threw his began to that it's factory starts at 1 end of the molecule and goes to the other and that vector in some sense tells you the direction orientation of quality now we we went from our 1st confirmation that this fall to our 2nd half of the nation 2 smaller change which way pointing at the end and happens to be the same but now we go on his 3rd confirmation in which inspectors now .period this and at the same time In the end and vector molecules has now also changed direction and way and so the lieutenant and vector which says something about which way the ball point in the changes orientations it could change when you change the engine and vector orientation which way and and vector points you were with rotations and if you're just changing the length of the vectors so it gets longer insurer that is what is called the renamed the lies inhaling exhaling world some useful minor detail suppose I go along with the polymer molecules and break into sentiments each of those segments because chunk of molecule is free to change which way it points and it can do that through internal motions however there is a constraint if I cannot over all of these little pieces which way each each 1 .period I have to start here and I have to get up there and there were a total of all of the little pieces is constrained because it has to be added to the end back In order to change which way the and together the 2 points I have to wait for the whole molecules to change direction to rotate now the whole fuel assimilate what it does not rotate freely like all planets around saw it does diffusion changes shape however the motive motion changes us from here to there is fairly slow the soul of all these little pieces their work has a heart problem of things but it hasn't heard a little bit which must stand up to to this and therefore each of these little pieces hasn't part of its direction which can only change when the whole molecule changes direction and therefore when we talk about motion during the direction of pointing along the Mall fuel there will be a fast peace because the molecule wiggle rear faster but I heard about the direction of the molecule plants is going to be relaxed only because acknowledgment rotates this is fact by 5 days so that was so we announce that we have ,comma molecule it's flabby if you imagine a
over a very long or boiled noodles in a hot water and the highest being while so Carolyn but the water is roiling and the notable was carried around the new rule changes shape if you look at the 2 ends of lot which direction it is from 1 end to the other it keeps changing and that sort of emotional polymer and perform I'm slightly oversimplifying in 1 respect namely I'm saying the molecule changes shape but it's not for most of what will be talking about driven motion warning applied shear or whatever instead it's simply a matter that the other the molecules not the absolute 0 the ad moved back and forth at random and this gives us the diffusion process OK so I have not talked about modes of molecular motions and I have talked about stock Meyer played a tight B and motions From the standpoint of this course we were interested in Help ,comma molecules ,comma solutions for example flowing into the viscosity the tight C motions where the say benzene rings just spinning around its upon etching backbone the Type C motions are not very good because they have a lot of very fast time scale the title be motions are not so important and the major issues how does the whole chain who are in large part described by the time a motion it's OK so we have now discussed molecular about but don't worry Julia and studying this but if we are interested in studies that we experimental method and when they actually give us information about the background about what is happening in solution and meets with the experimental methods do used to tell us how rapidly the molecules reorient so what are the major methods were going to talk about the major revenue thought about part of BHC and time to resolve polarization an analog nuclear magnetic resonance on each of these gives different information because of physical processes that leads to something happening is different fruits 3 shorts motion all that and Elmora gives us information on a very local this is scale that is we have for example there is little chance of molecule and since there is peace of molecules here there's a chemical bomb there which has a direction and what Panama's directly sensitive to use the orientation of the direction directions space of their bonds with respect to the local magnetic field now and ,comma has limitations relative to the speed of which things that happen that Panama frequencies are quite low they are well when I was an undergraduate at loose ends of megahertz and when I was 1st grade a faculty member you were talking about a few hundred megahertz and people are now creeping up on a gigahertz however the times of less useful in a series of frequency so many cycles or there isn't time how which is the timescale for and these are inversely related so if I say I am looking at something in the frequency range of 1 gigahertz that's approximately like saying I'm working on time scale of manners that that relationship is slightly in precise because time domain and frequency domain were not the same thing however what we can get out of them and I discussed this in more detail in the book and give you some references also if you're really interested in Montana is a very nice weather page from a fellow at of the University of Rochester which really explains very clearly how all that work on a bit of a friend of the president all of Indiana in the various issue is what you can do with him on the pullout the characteristic time town which is how long the molecule fond remembrances pointing in its original director felt that the statement there is a time is imprecise 1st of all it's not all these bonds sit there and that much time later they all fled 90 degrees the motions of defuses like my way I point my thing and furthermore Exxon as time goes on the molecules less and less likely to be appointed its original direction and if you wait long enough like he analysts the
direction of the fondest plated has nothing to do with the direction in which started that there was the system has a memory in this small molecular bonds so to speak for guess which way it was originally .period and Washington's extract out is a relaxation for a single I'm so that's bond reorientation the next thing 1 can do do is talk about time-resolved polarization the 1st flight to emphasize is that for many chains when you're doing time-resolved polarization measurement unit produced a polymer that is specific for the experiment in which you have inserted chemical group into the center and the chemical who group was called home for what is this what sort of experimented with cocaine we send them a wholesome white Minnesota light is is brighter than it is right for a very short period of time like Peco said you can do this with pulsed laser alternative the light comes in and defines the problem for being in precise as to what is there the more fuel and it excites the died all a transition dipole the molecules and it takes this molecule and it moves it to an excited electronic state so that in the molecule on a little piece of the molecule to actually use the little piece of a molecule is sitting there is absorbed light of this frequency now it well of you wearing little while you get fluorescence the molecules absorb light and if you waited their whole life comes out again it's like 1 of these things is close .period if you leave someone 1 of this is fluorescence however modesty features of fluorescence Witcher a little more elaborate than just blows .period we send in that has a polarization of we call vertical by which we mean we have a table on which the apparatus sitting we have a light source we have samples we have detected camera and the vertical axis is perpendicular to the plane of the table and perpendicular to the plane of the incident like the 1 the outbound flight well it's a mixture of vertically polarized light and horizontally polarized light why is the case what the molecular processes were sending in vertically polarized light it's absorbed by the material on the weak side 8 was called transition I material however the transition dipole managerial Castellon in the direction fixed by the organic structure material so in general while I had some direction like this which is not the the same as the direction the incident light then when his wife it's really amended by the dipole the scattered light will come out he played with the polarization which I'm indicating here like this and so I set off camera and manage measure the intensity of polarized light that way we're there well "quotation mark polarization of the nation's like this so I put my Polaroid filter on or whatever lies with this way or that way I measure a certain amount of intensity in each direction the merger will now we come to the complicated part this time attached molecule culture you how however there as the molecule reorient the Stuckmeyer a B and C processes come in and change the direction of of the stock actually it's only 88 process and will show you how best known world all of the important issue is that if I fired a series of people 2nd balls and they ask What is the direction of of the white polarization right after I said Paulson well it's basically like this however if I sit and wait as time goes on and why wait very long Peco said insists on manner said I waste time scale on which the the molecule reorientate initially this it's difficult by was facing 1 way but as time goes on the direction of the died changes the dipole forgets which way pointing originally and then the light that reaches the camera has no polarization it is this fluorescent molecules mindset of photon but the photon eventually is equally likely to be
polarized 1 way or the other and there is a time scale on which the amid light starts being without being polarized and if you sit and wait for the molecule forgets which wanes .period and you can actually measure the reorientation of that is to say this is a factor all these the bacteria which had some direction at time 0 lawmakers staff rather than some direction from the and we average what we discoveries that time if he is 0 but I've always points along its operational direction has been but his friends the final measure up what happens there is an orientation functions With his case and so this function the phases time those on and molecule forgets about which way it's quite so far so good so there is time resolved polarization the gives information about an organic group announcing not just a single bond someone is giving information about slightly larger extent there's another feature that has not played for organic molecules of air to worry about that however here's a piece of a backbone chain that's not all cost polymers don't have current current problems the backbone but it's a hypothetical example and what I do is I stated in here the problem for the most vulnerable of fuels were don't really have a problem us they don't have something that does a nice job of absorbing light remaining so we take an organic group which is something like anthracene it's colleges of benzene and we say the organic growth this year and we choose the organic group so that the on transition indictable points like that and that's matter of doing organic chemistry that is you have been factor putting here organic molecules I can find organic molecules which will call to bonds as indicated and the transition dipole will lie like this but also find somewhere transition dipole points this way it's simply a matter of doing good organic chemistry and getting the right organic solutes now in order to do this I actually have to to do organic synthesis that is I have to find the appropriate problem I have that identified folders I was hearing here and I have new chemical synthesis to state this thing in where I want most of the results that you will see in the book referred situation and what types of this thing and stop Indian right to dead center molecules so this and this change are exactly the same way however there are a few experiments in which carries small fuel and status through onto warning so we can look at how the man moves as opposed to the set because the dipole lies this way and it really does my life is the only way the direction of the dipole be relaxed is a stark Meyer high emotion and that is the whole chain has to rotate and over and the were this local PCs to be rotated and over on anything that those a crankshaft light emotions that we are not sensitive let me draw little country history reverence said Panama the sensitive in Singapore to CAG bond directions ch on points that way the CH bond direction substantially rotated by crankshaft motions have been moved its naira wrote reflects the all this case by a motion because there's nothing to rotate around the exercise no show of course you could say I will see some of the that thing out here and have a proton here and then if we flipped the molecule like this the direction of this ch on access can be be wet and since Adam unwarranted very sensitive and 2 mobile unit actually washed separately the relaxation of each of upon direction however in this case we have synthesized something in which the molecules excitation died all lies along here and therefore if the molecule never changed direction we never see any relaxation and is the polarization of the emitted light that change because the law school can rotate and change shape what we find is that the direction of the bond axis changes as time goes on and therefore the amount of people authorization OK
that's I'm results polarization if you think about it you realize there is a limitation on mastectomy and a limitation on this technique is this is a fluorescent molecules you ,comma light into it and as time goes on because of quantum mechanical processes the light is readmitted this molecule has a lifetime on which stores areas as time goes on when you go beyond that lifetime is as you go beyond exponentially he
said of following photo much energy is stored and if you go way beyond the lifetime all of the fluorescent molecules have reinvented and there is no more light coming out of it and therefore time limit on water actually seeing the reorientation with this method and the time limit is the organic molecule has to have a sufficiently long life Of course organic molecules are very cooperative in this respect and have long lifetimes but you should realize that there is this other process going on at the same time as the process interested right now we do th the following items can time-resolved polarization basically says I have to factor in the mold and the factory changes direct BH scaring know something else here is shown all by sending lightly from standing in light waves the light weight and acts on the Mall and solvent around and the white waves creates without applying electrical field I polarized more I don't permanently polarizes idea that oscillating died oscillating the frequency and his wife Tessa around now going to do this with polarized light the light is polarized in the climate of black soldiers of electric field light pointing this way there is no electrical field pointing out of work toward you so clearly the light comes in the electrical field Exxon molecule tone 1 way only electrons the opposite way on nuclei and because it does this he created dipole moment in the model it creates an oscillating died and went to lastly died polls do after electrical dipole the oscillates some frequency it emits electromagnetic radiation here mind at the same frequency are the lowest frequency version of this this was actually done as an experiment a century ago test Maxwell's equations if you take step dipole moment of Boris charge plus at 1 and 2 -minus at the other end use standard you will emit radio waves spinning frequency because it's an oscillating died you really works but we don't have to do this so we just stop sending in visible light and we created by holders of some angle with respect to the point polarization when he died called menace the guy full minutes like that hasn't this polarization not it's related to the polarization of the incident like that it's not the same in particular the polarization of the Seattle Light is determined by the polarization of the the incident light and there will be a object that states here a mathematical objects and changes the incident last year in the final this object is 8th Revised 3 matrix cancer and you do well later small locations and the direction of the directions the scattered light polarization is determined by the orientation of the smaller and it's determined by the fact that the molecule title it's not just wide enough with the home title With the incident the number ways of being this for example if you have a perfect sphere because of symmetry if there's nothing inside the Sphere to give orientation European manufacturer you put manufacturer or molecules scientists fear on but if we didn't do anything like that it's just sphere and the scary light will have the same polarization is the incident now what happens well there's scattered light coming out toward you and some of it has polarization perpendicular to the incident polarization however this molecule is moving diffusing history of segmental or reorientation and because this molecule is more of a the brightness of the scattered light he exchanging because of disorientation keeps changing and therefore the angle between this object which is really a 3 by 3 writers in this incident like the exchange so the brightness of the method might be polarized brightness changes and it changes on the time scale on which this molecule so find characterized the fluctuations the changes up and down and the brightness of the scattered light the polarized light I wouldn't characterize how long it takes this molecule to forget which way it is .period now what sort of time scales are we talking about well we are talking about time scale along with molecular reorientation workers so there will be peace that occurs very very fast like on the coast at times but there'll be another piece stock higher Friday there will be a small piece that requires the whole molecule to changes directions to reorient and that can take place on time scales down accuracy this technique does not have any of the problems that mom and time-resolved polarization with natural processes that keep you from seeing what's going on in this status is stable this is stable and even if the reorientation is very slow you can track at just as straightforwardly as you would if you suspect so problem I mentioned with time-resolved polarization where the I Have a promo for probable for his lifetime and eventually that lifetime gives you a headache trying to get the experiment work here we don't have a problem at all then no I'm have not described methods for measuring or anything that giving you a very simplified description I don't think I have said this thing that goes that was true worsen fight all as I said before next time for this chapter 6 redirect 14 and Stosur last now and hopefully we will be ready to talk about without having to look over in OK so we're talking about reorientation and the question is what physical processes actually cause reorientation what physical processes and give us the relaxations that these methods I measure well the simplest thing you could do do was to say yeah I talk about stock Meyer ABC How do you know that I'm right How do you know that that's a reasonable description how do you know that it's local train motions that are causing reorient Anderson was the answer the pretend I'm modest that you or at the least and their corresponding measurements with other techniques is the measure of the times required for the reorientation personnel that's a typical tough it's not the way exactly that kind of thing we looked 19 agrees it's a gradual process and what you find is that this is candidates from the molecular weight of Paul it is to make the polymer longer you make the the polymer shorter we'll get to the within reason limitation of that and nothing happens to the relaxation what's very racist on what does that tell us it tells us that we're looking at some little piece of Polish physically and followed peaceful looking at health care very much about what's out here however we know from white variety of techniques that if you have a whole chain when asked how long does it take for the whole change reorient along the chain is the slower the head over heels motion and there was a statement that we're seeing a process that is more or less independent from white to gray Paul tells us that we're seeing a local for the most part a local chain motion With BHC you can do it better than that and you can also look processes on quite different time scales and if you go out there so that you're looking at chains that are less than 2 words thousands although you're walking change their efforts polystyrene tens of some units along very short claims that reorientation time does depend on polymer molecular weight the reason for that is that the changes were insured the process by which it said actually reorient the whole chain reorient can take contributes significantly for how long it takes for this little piece to so therefore if you look at very short chains you actually can see a molecular weight and this statement you can see a molecular weight dependence thousands of health care is a little piece of Paul McShane orientation it "quotation mark that time orientation time prolonged take from all of you change direction is not the same as if were there Hey Mama floating free in solution it's not the same because the 2 ends at all stuff on each side end the changes direction after stuff on each side therefore there is coupling between monomers and stuff on each side all this number tells you roughly speaking insults says how far out of their coupling extends if you go all out for a the motions of this piece the local motions are independent of what's happening out here but there's a distance within the motion of this piece and emotions of the neighboring pieces are coupled to each other it is as if you had a very long line of people a straight line 1 line and they were all holding hands well as I'm holding hands with 2 people I can't do this very much but there group of us we can move backwards and forwards and I'm in the right place I can enter and the question is how far along the the line is it before what we're doing and what the other people are doing doesn't care much about and some numbers like this all that is not very precise numbers for 7 innings OK let us Bush and let us what sort of information we get our experiments that love used kind enough to remind the last time that I kind of careful I download pages for final manuscript which have different nature lovers and there books so I'm going to start staying with figure numbers and we're going to put the figure at 6 4 and who questioned the just talking about the Indian government I'm going to go out and have some assistance to the launching of the but the question was if I have to start all over again what I want is what happens if I have to stop all you can do a lot of it and in the absence of getting out there and also the things we need pieces coming out here short groups on the answer is the rotation time is determined by the molecular structure and 1 of the things that happens ,comma chair sector and the soft side it will move as quickly as it also was quickly because the science groups will get in each other's way you can also have a polymer chain which you have things coming off work .period all and this fact Ameristar will have some effect on emotion here I here affected Stockholm will be added nearly so much yeah OK all right so we will try to help figure 6 the actual and 6 days after all look sale relaxation time and this is they are home time-resolved polarization and you notice the time scales were looking at in nanoseconds tens of hundreds and he's results primarily of POV as part of where there is a measurement of how house and this is a function of the concentration of these experiments actually go off to something like all 25 grand ballroom program system that's about it most things are about the same density and therefore people follow eyes corresponds to roughly 50 per cent of of the system being called molecule and 50 per cent of the system being sold what you observed fuel the graft is that there is this region in which the relaxation time increases not very much a factor of 2 or something like that and when we get up to about overweight 3 Grandpa Graham 300 grams per the year and above that the relaxation time increases vary from medically you see was there if you think about that massacre we've seen before because if you look at the discussion of solvent motion In the previous chapter this is a little piece polymer reorienting but if you look at the discussion of solving most for solving motion we struggled loans and debt about the same place and then there is quite a dramatic change in how rapidly the souls and the and it can only move much more slowly in most cities so what we say is we do this experiment and she called the constraints that interference solid motion concentrations are replicated we asked how rapidly we can get of little pieces of polishing reordering OK yes of course this is a matter of time want part of the question is what causes this physical effects well the 1st point is since it affects the solvent molecules as well as change we can't very well say it's entanglement because the solvent molecules on hand furthermore all the entangled believe entanglements have you intend to change the chip entanglements last very long time relative to this so the Pope polymeric background perhaps can be be approximated the large-scale structures the station so you sort of have asked for what happens about this concentration the following is calculation which I only India at UC estimate of something that happens here in Parliament for its handling of a cross-section of the solutions so this is Paula oil giants sliced like a piece of sausage it's really coming out of the border toward the if we were in melts like these changes very close together near now I'm going to put the all Janus Orion is accident so you can see it as a shaky start all there isn't a typical distance signed between 2 polymer chains here CSI is very tiny it's not 0 because they're panicking constraints and this is liquid but here excited somewhat larger there is also a time when people inside his car of all of the Soul the argument of giving is in fact based on paper by tying Ted tells this is not my book because the paper recent macromolecules but this last fall and found the letter and they discussed this they don't quite get it gives the following argument they can give the wide-scale recently to the area there is a concentration of which typical spacing between vulnerable peoples yet small enough solvents can get through gap and this space against small enough to solve all world's can pass through the gap suddenly solvent molecules don't flow freely and all sorts of dynamics must change well how big is this yeah I'm going to be here it's too small well what sort of concentration of media with lost yet France it's a question here is 1 of following molecules here's the lessons for the next came out With this side the and here is historical around Beijing the following campaign has some radius are this guy that is he had size formal you should realize he's a very approximate .period the cross-sectional area all the following day level is higher square it by surprise at once the cross-sectional area of this big thing it's something like high water was I'm sorry little or was clear Laura to square yeah the ratio of Eastern numbers around mergers very very long almost infinitely long relative to this picture this ratio is approximately the fraction of the the volume of the solution that is filled with Paul there is this area fires in life is the volume of Paula in the picture this is the volume Of all the cover the total volume of the solution and so this ratio is a very approximately find the volume fraction of former when you get this transition well atypical polymer oil is somewhat bigger than a typical Salford fall although it obviously depends on which called and which solved but if you put in numbers like this year the June 28 reasonable numbers for little Laurence Baker got you discover this number is told Suarez like that left it's not at its 20th more attendants and it's not 90 per cent is something always vaguely life and sell this discontinuity which is transition where you all of which is actually seen in a variety of dynamic processes corresponds approximately to the point which solvent molecules can no longer squeezed between flow freely between polymer chains and also the space which if I have another following while his wife is like this it runs into problems getting between its 2 neighbors because there's not insist on role so that actually appears to be what its ideas from we have now moved from the paper which the book which is beginning a discussion I started writing 2006 so 2006 2001 we have now gone into something which is vaporized Britain which is passing back and forth between me and the Journal referees so we analysis postponing its research yeah but there appears to be a reasonable explanation if you read through the fall since I haven't seen that in the idea of myself and referred to the transition toward balanced Allensworth and say in the book that I don't know what it was well that's change we make progress OK last portion and we will push ahead after 3 years 6 . 1 per work by Waldo and collaborators in most of these cases I do not know of the people's life and personal there will be members of some of whom were great students and we refer but favored by 1st offer any issue is supposed to look to get relaxation time versus the molecular weight qualitatively what was found was that if we all look at the relaxation time elected by the hall noted that would there's not much of an effect if we look at a relaxation and relaxation time in the solvent relaxation time increases so long you to freeze the molecular weight and I'm sure emphasizes a key factor is much weaker than say the effect of solvent viscosity but there is a modest effect anyone can then ask Well that's very interesting how can we possibly explain and what was going was due calculations can polish we're going to change the solvent quality West surveys clashed briefly hands if you've never heard of discussion of souls all good solvent vapors all yes OK but while the question is if we had a good soldier the chains rather may interact with their neighbors With solvent and on on the ball and chain oil expanded were in favor solvent change in tracts if we are a solvent catastrophic failure eventually things fall out of solution for you get protein molecules called reflect the walls of of proteins it is chains of amino acids the waters were solved the proteins are happy to dissolve but only at rolled up the opposite of what they do this is seen as white if you have any white and heated up for example those who have been caught in the act like he's happy To be nature and even the nature is for example you put it in hot water it seeks to all sorts of services Donohue's sold stakes all sorts of services and their cooking career which has been known for millennia reasons people the region of why is that if you were doing eggs you want to wash the dishes and cold water 1st to get the egg white offer it becomes much harder than what you see all the chemistry is actually good for something OK in any of the wall-to-wall albeit with say I was looking at a typical he's the poll not the center but it's typical chains that and I will ask How the density of chains settlements near the famed sentiment and looking at changes as I change the polymer molecular weight this is not the same as saying I have polymer chain I counter the tangible density of polymer change segments with center and you may have seen it was calculated the senator calculation this is a different calculation it's a much harder calculations do for example computer-simulated any gives a different answer and the answer is if you have a pall oil you need a good solve the density of sentiments this change does not change the future of fall molecular weight if you have polymer oil the solvent and they asked how many other things that concern this form of all the way the number of change segments goes I should stress that this is the density of change sentiments were examples of this 1 for this 1 the post technical change sentiment not under close to the middle of the chain it's 2 different calculations and you want to realize the difference in distinct and so on this effect is explained as well you have chains that trying to move and other nearby segments they bump into each other the hydrodynamic interactions they interfere with each other's motion the guest of the economy in Europe with the skills the you will have to consult the original papers but we're talking assume on I said it was a few monomer diameters you would be wildly different from then on what may have been dollars to harm calculates a density in year contract but look at the original papers OK so let us push ahead and will push ahead from figures 6 . 1 and script figure 6 . 2 and will then eventually figure 6 . 3 and 6 . 4 so new experiment and we take a home :colon and we're going to take a polymer that is stock to Woodsville so there is always changing and these characters in another chain and the at the scene arranged so that the transition dipole we do fluorescence the anthracene points exactly along the chain so rotation like this there's nothing Our it's not grew only it's not my entire rotation motion in Group relax which way this thing is .period so we are in a series of different and then saying we're sold if we change the temperature we change the viscosity of salt and so the simplest reaction that change the reaction of the viscosity of the soul of the innocently and not quite correctly the prospect this is a diffusion process is all about universally as the viscosity of the assault was guests so how can you change the viscosity of a solvable there are 2 things you can change you can't change the temperature of Expedia's 6 . 3 and you can also go in and change the pressure because if you have solvent and you run up pressure its ability to flow changes sometimes quite substantial Have you actually if you're doing High pressures "quotation mark allowing you actually have to think about these things were will convene negative consequences and we then asked Well OK we have done this How does the reorientation time dependent on temperature and pressure Wisconsin and the answer from a whole series of pastries and I mentioned arm I mentioned at all in the whole series papers about which very different things which are very clever papers that I sent them somehow 0 which has just come out and then analysts viscosity to power a and then there is an exponential factor leading song and the cost of the DEA Over all right the gas constant horror that also be written this and there is what could be his problems in some circles to be called an activation and niece of the day In the southern are constants that don't care which sold during which temperatures here and this is the 10th and there is there is a background temperature and pressure the presence of how fast bowler moved that does not care about solvent at all and then be written in this form and then hiding outside of this there is number the depends on the viscosity some time this is what is called the general tournament the latest from originally Dutch physicist going there In the past 60 years at this point we actually was talking about a completely different physical phenomena and what he said was the rate at which the process can occur will be inverse into the viscosity of the salt and whatever whatever process you were talking about what the rate which something deeper at the University viscosity at the time it takes the media and the viscosity of the same thing ,comma installations without generalized we have paid for war the generalized college relations has viscosity some power however when we say we're changing the viscosity of soul we change the temperature and the pressure we also changed how much energy is available for example who broke the chemical bond polymer around its axis we all we change all issues that are associated with the ability of the Paul removed in ways that have nothing to do with the salt so we know all that and you get to 6 . freight and what figure 6 . 3 shows this this reorientation time versus viscosity and fortunately the original authors to huge Nova measurements so there are lots and lots of thoughts on that and what you see is but there is a segment of the data were a is about what it is the time increases roughly linearly discussed in this system that's something like concerns boys there's crossover which is extremely sharp and we have viscosity the powerfully that I recall today that figure at all .period success now we saw that figure we talked about solving discusses the 2 namely if you measure connectivity you were diffusion small rules and biscuits sold you get a graph looks almost exactly like 6 . 3 guest happens different solvent the crossover occurs in different viscosity but you have a low viscosity region were a years-long behind us in the region where a happens in it's in this case it's two-thirds or if you read the chapter you was discover the other cases where the viscosity workday is more like all . 5 depending on which physical technique you used to measure rotation of watching the on any care about the physical technique the answer is but you looking at this all of the center his hands Racine's used benzene rings it's certain modest number of rainstorms across if you're looking at the polarized light scary you're looking at that our goal of persistent slightly longer somewhat larger if you did this with any of our had over an hour as do this all Americans not 5 looking at seeking chemical bombs chemical bombs small and therefore you look on different distance scales and coupling of the emotion in his custody of change as to make the object of looking at the couple and become to the viscosity become strong the so that is a description all of the generalized promise relations however story remember there is any more data and it does show this and it's prevented more data base more like half of the year the animal owners looking at a single bond which is very small and the occult and this Garcetti's leaders the time-resolved polarization here's an interesting it's bigger and he is large and serious remember I'm also the attention is room AT and center chain you should not be surprised to learn that the relaxation times for a man who on OK let's guesses and relaxation times for the and group going to be smaller or larger than the relaxation times the anyone against well it's in book the answer costs smaller because of I'm out here in I'm much freer fly back and forth and find all so that's the answer to that the last thing we can do the only way to change the viscosity will change the viscosity not by changing the temperature were changing the pressure for change in which small will solve week instead we will measure reflects this relaxation 1st concentrate and if you already have solvers you see the effect we showed year 6 . 1 where there is a change 400 gram leaders however if polymers Baldy universal solvent molecules can move laterally on what what instead fired power over his life for what appeared to be seen current smooth curves Foreign Affair stretched exponential it's OK we're almost out of time I have spent the day discussing home emotional GE the little pieces of change said we will now advance tomorrow Weld's Wednesday we will advance Chapter 7 and we will discuss a dielectric relaxation dielectric relaxation is incredibly powerful tools for studying polymer dynamics it has not been used in nearly as much as it merits given how powerful technique and dielectric relaxation gives you everything from motion short segments of promotional change the size of the chain internal loads those all sorts of things as we will see starting next time please read chapters 7 before next time we're gonna class dismissed
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Metadaten

Formale Metadaten

Titel 7 Segmental Motion
Serientitel Classes in Polymer Dynamics
Teil 7
Anzahl der Teile 30 (Lecture 2 missing)
Autor Phillies, George
Lizenz CC-Namensnennung 3.0 Unported:
Sie dürfen das Werk bzw. den Inhalt zu jedem legalen Zweck nutzen, verändern und in unveränderter oder veränderter Form vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen.
DOI 10.5446/16233
Herausgeber Phillies, George
Erscheinungsjahr 2012
Sprache Englisch

Inhaltliche Metadaten

Fachgebiet Physik
Abstract Lecture 7 - Segmental motion. George Phillies lectures on polymer dynamics based on his book "Phenomenology of Polymer Solution Dynamics" (Cambridge University Press, 2011).

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